Inherited Disorders and Birth Defects

My grandson has developmental delays

02/12/2007

Question:

He is 10 months old. He has nystagmus, stridor, laryngomalacia, reflux. He has no pincer grasp and is not crawling or pulling up at all. MRI and EEG at six months and all blood work and urine tests came back normal except for a slight elevation in lactic acid. Could this be PMD? Perlizaeus-Merzbacher Disease? Also, I heard that sometimes the MRI that was normal at 6 or 8 months will all of a sudden at 12 or 18 months finally begin to show what the problem is. Is this true?

Answer:

This question has been forwarded by Children's Health:

Pelizaeus-Merzbacher disease (PMD) is a genetic disorder of the central nervous system (the brain and spinal cord) in which the covering of the nerves - the myelin sheath - is not formed properly. The myelin sheath is made up of fat and protein that acts as an insulator on the nerves (axons) in the brain and spinal cord.

The disease is caused by changes (mutations) in a gene called proteolipid protein 1 (PLP1). The PLP1 gene is on the X chromosome so that most affected individuals are males who inherit the abnormal gene from their mothers.

Pelizaeus-Merzbacher disease usually begins during infancy. Clinical features include nystagmus (involuntary movements of the eyes), lack of muscle tone (hypotonia), with tremors of the head developing later as well as spasticity. There delays in motor and intellectual development. Some babies can have stridor (labored and noisy breathing).

Because myelination of the nerves in the CNS happens over the first two years of life, problems may not be seen on an MRI that is done at a few months of age, but can be seen on MRI between one and two years of age.

However, I cannot make a diagnosis for your grandson as there are other causes for the problems you describe. Your grandson's doctors are the appropriate people to make a diagnosis for him and his parents. If PMD is diagnosed, I would recommend that your grandson's parents talk with a geneticist as this is a hereditary disorder which would be important for them to discuss. They can locate a genetics center near them at the National Society of Genetic Counselors' Resource Center website below.

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